Ineffable Intelligence closes Europe's largest seed at $1.1B, $5.1B valuation, led by Sequoia & Lightspeed

Ineffable Intelligence, a London-based AI lab founded by David Silver (former leader of DeepMind's reinforcement learning team), closed Europe's largest ever seed round at $1.1 billion, valuing the company at $5.1 billion post-money. The round was co-led by Sequoia (with partners Alfred Lin and Sonya Huang) and Lightspeed Venture Partners, with participation from NVIDIA (contributing at least $250 million), Google Ventures, DST Global, Index Ventures, the UK's Sovereign AI Fund, and the British Business Bank ($20 million).

Ineffable, incorporated in November 2025 with Silver as director as of January 2026, is pursuing a reinforcement learning-focused approach to superintelligence. The company aims to build a 'superlearner' capable of discovering knowledge and skills autonomously without relying on human-generated training data—leveraging techniques similar to those behind AlphaGo and AlphaZero, both of which Silver developed at DeepMind. The company has no product, no revenue, and no public roadmap but is backed by the credibility of Silver's track record: he led development of three of the most celebrated AI systems in history.

For investors and practitioners, the round exemplifies a 2025-26 market shift away from valuing current capabilities toward betting on founder credibility and research tractability. The $1.1 billion seed exceeds typical mega-rounds and signals sovereign capital (UK, France, UAE, Saudi Arabia) actively competing for compute-heavy AI labs. Silver has pledged to donate 100% of his personal proceeds from Ineffable to charity via Founders Pledge. The move underscores London's emergence as a venture hub for DeepMind-alumni-founded AI labs.